Caption: Spark discharge. Exposed wires of a three-pin plug with a spark discharge between the live and neutral wires. The spark travels from the brown live wire to the neutral blue wire. Each wire connects to the appropriate pin in the standard three-pin plug used to connect appliances to the electricity supply. The green and yellow earth wire is an electrical connection between the appliance and the ground. In the event of a fault in the appliance the electrical current flows to earth causing no harm to the user.